Transmissible spongiform encephalopathies (TSEs) are progressive, fatal diseases affecting the nervous system, causing spongy degeneration in the brain and spinal cord. TSEs include bovine spongiform encephalopathy (BSE or mad cow disease) in cattle, scrapie in sheep, chronic wasting disease in deer and elk, and variant Creutzfeldt-Jakob disease (vCJD) in humans. Although the exact cause of TSEs is unknown, the infectious agent is suspected to be a prion, a misfolded protein which has the ability to self-replicate and accumulate in neural tissue, eventually causing tissue damage and cell death. There is no treatment or vaccine currently available for the disease. Prions are notoriously resistant to routine methods of decontamination.
BSE was first diagnosed in 1986 in the United Kingdom where the majority of the world's cases have occurred. The first North American cases were discovered in 2003. Consumption by cattle of BSE-contaminated ruminant proteins in animal feed has been cited as the most likely means of transmission. Such outbreaks have had major implications for the North American beef industries since foreign markets have closed their borders to beef and cattle exports. Surveillance programs to monitor and assess BSE in cattle herds have been implemented to provide early detection and contain any possible spread in order to keep BSE out of the food supplies of both animals and humans. In humans, vCJD is thought to be linked to the consumption of meat products derived from BSE-infected cattle.
Prior to the emergence of BSE, the primary use for animal protein by-products was as feed ingredients for cattle, poultry, pets and aquaculture in the form of meat and bone meal, meat meal and blood meal. Subsequently, specific cattle tissues, known as specified risk materials (SRM), have been banned from use in animal feed, pet food and fertilizers, and have been accumulating into landfills at a rate of about 5000 tons per week.
Rendering is a process whereby waste is “cooked” into ingredients for a wide range of industrial and consumer goods. Regulatory actions to strengthen safeguards against BSE portend significant changes in renderer's business practices, and the value of their products. If inedible animal byproducts have fewer market outlets, the overall economic value of the animal to the producer can decline, and questions arise about how to safely dispose of the SRM. The necessary restructuring of the rendering processing lines to handle SRM and non-SRM in separate lines and costs associated with SRM storing, transporting, and disposal fees have adversely affected profitability to operators and negatively impacted the beef industry.
Therefore, there is a need in the art for methods of safely handling SRMs and converting animal byproducts into useful products.